This disclosure relates generally to online systems, and more specifically to predicting a level of knowledge that a user of an online system has about a topic associated with a set of content items maintained in the online system.
An online system allows its users to connect and communicate with other online system users. Users create profiles in the online system that are tied to their identities and include information about the users, such as interests and demographic information. The users may be individuals or entities such as corporations or charities. Because of the popularity of online systems and the significant amount of user-specific information maintained in online systems, an online system provides an ideal forum for content-providing users to share content by creating content items (e.g., advertisements) for presentation to additional online system users. For example, content-providing users may share photos or videos they have uploaded by creating content items that include the photos or videos that are presented to additional users to whom they are connected in the online system. By allowing content-providing users to create content items for presentation to additional online system users, an online system also provides abundant opportunities to persuade online system users to take various actions and/or to increase awareness about products, services, opinions, or causes among online system users. For example, if a content-providing user of the online system who volunteers for a non-profit organization creates a content item encouraging additional online system users to volunteer for the non-profit organization, the online system may present the content item to these additional online system users.
Conventionally, online systems generate revenue by displaying content to their users. For example, an online system may charge advertisers for each presentation of an advertisement to an online system user (i.e., each “impression”) or for each interaction with an advertisement by an online system user (e.g., each click on the advertisement, each purchase made as a result of clicking through the advertisement, etc.). Furthermore, by presenting content that encourages user engagement with online systems, online systems may increase the number of opportunities they have to generate revenue. For example, if an online system user scrolls through a newsfeed to view content that captures the user's interest, advertisements that are interspersed in the newsfeed also may be presented to the user.
To present content that encourages user engagement with online systems, online systems may select content items for presentation to online system users that are likely to be relevant to the users. Online systems may do so by selecting the content items based on targeting criteria associated with the content items that identify online system users who are likely to have an interest in the content items. For example, a content item maintained in the online system for bakeware may be associated with targeting criteria that identify online system users who have expressed an interest in baking (e.g., users whose user profiles indicate that the users' hobbies include baking, users whose profiles indicate that the users' occupations are related to baking, users who previously interacted with content items associated with baking, etc.). In this example, upon identifying an opportunity to present a content item to a user of the online system, the online system may select the content item for presentation to the user if attributes for the user satisfy one or more targeting criteria associated with the content item.
However, a content item that is associated with targeting criteria satisfied by users of the online system may have varying degrees of relevance to the users based on the users' knowledge about one or more topics associated with the content item. For example, online system users who have recently taken up jewelry making are more likely to have an interest in supplies required for basic jewelry-making techniques (e.g., glass beads, wire, pliers, etc.) than in supplies required for advanced jewelry-making techniques (e.g., gemstones, solder, blow torches, etc.) while the opposite is likely to be true for online system users who have been making jewelry for several years. In this example, suppose that a content-providing user of the online system has created a first content item associated with supplies required for basic jewelry-making techniques and a second content item associated with supplies required for advanced jewelry-making techniques and has associated both content items with targeting criteria that identify online system users who have expressed an interest in jewelry making. In the above example, even though the first content item and the second content item are likely to be relevant to different online system users based on their level of knowledge about the topic of jewelry making, the online system may be unable to identify these users, rendering the content-providing user unable to associate more specific targeting criteria with the content items that would allow the online system to target the presentation of the content items to the users based on their level of knowledge about jewelry making. Therefore, online systems may waste opportunities to present content items to the online system users that are more likely to be relevant to the users based on their level of knowledge about various topics associated with the content items.